The present invention relates to a catalyst for producing a polyurethane, and a process for producing a polyurethane in which the catalyst is used, such as a flexible, rigid or semi-rigid polyurethane foam or a polyurethane elastomer. More specifically, the present invention relates to a process for producing a polyurethane such as a polyurethane foam which can be used as heat insulating materials for construction materials, electric refrigerators, refrigerated warehouses, baths and the like, interior materials for automobiles, furnishings, cushioning materials for beddings, various sealing materials and the like, and a catalyst for producing a polyurethane used therefor.
As a catalyst used in the production of a polyurethane, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylethylenediamine and N,N,Nxe2x80x2,Nxe2x80x2-tetramethylpropylenediamine have been widely used because of their appropriate catalytic activity and excellent moldability. However, there are serious defects in public health when the catalysts are used since the catalysts not only exhibit bad stimulative smells but also generate eye rainbow (the state where a rainbow is observed) due to the vapor of the catalyst during the operation for the production.
In order to eliminate these defects, there has been proposed a tertiary amine catalyst such as 1,4-diazabicyclo[2.2.2]octane or N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexamethylenediamine. The effects due to the catalysts can be recognized to some extent. However, it could not yet have been said that the effects are sufficient. Also, since these tertiary amine catalysts would not be incorporated into the polyurethane via a chemical bond during the urethanation, there are some defects in the catalysts such that there occur inconvenient results such as a so-called xe2x80x9cvinyl-stainingxe2x80x9d which is caused by the discoloration of a vinyl chloride resin sheet used as a substrate, and a so-called xe2x80x9cfoggingxe2x80x9d meaning the fogging of window glass of an automobile due to the catalyst vapor diffused from the polyurethane.
As an amine catalyst which is incorporated into the polyurethane during the urethanation, there has been proposed a tertiary amine catalyst having in its molecule a hydroxyl group and an amino group reactive with isocyanate group. When the tertiary amine catalyst is used, the problems in vinyl-staining and fogging are solved. However, the molecular structure of the polyurethane would be changed by the amine catalyst, so that there are some defects in heat resistance such that the strength is lowered especially when the polyurethane is exposed to an atmosphere having a high temperature for a long period of time, and that the polyurethane is colored.
On the other hand, a rigid polyurethane foam has been used as heat insulating materials for construction materials, electric refrigerators, refrigerated warehouses, baths and pipes because of its excellent heat insulation.
When the polyurethane foam is used, for instance, as heat insulating materials for house or building construction materials, the polyurethane foam has been produced by mixing a component comprising a polyol as a main component with a component comprising a polyisocyanate as a main component, spraying the resulting mixture to a desired site such as wall surface or ceiling in the construction site of a house or building with a spray machine or the like to foam, and curing the foam.
When the polyurethane foam is formed in a manner as described above, peculiar strong odor based on the used tertiary amine catalyst worsens the working environment. Moreover, since the unreacted tertiary amine catalyst remains in the polyurethane foam even after molding, there are some problems in public health such as odor caused by the release and dispersion of the tertiary amine catalyst from the polyurethane foam. Recently, as a catalyst for producing a polyurethane which causes little problem in public health, there has been proposed a tertiary amine catalyst having a hydroxyl group in its molecule for the purpose of the avoidance of vinyl-staining and fogging (Japanese Patent Laid-Open Nos. Sho 62-115017 and Sho 61-252219).
When the tertiary amine catalyst having a hydroxyl group in its molecule is used in the production of the polyurethane foam, the problem regarding odor is eliminated. However, since the reactivity of the polyol component with the isocyanate component used in the production of the polyurethane foam is low at low temperatures, a long period of time is required for the production. Especially, when the polyurethane foam is formed by means of spraying, problems such as dripping would be caused. Also, there are some defects such that heat of the polyurethane foam generated during the production is robbed off by the air, and that the reaction is less likely to proceed, so that the compressive strength is lowered and its dimensional stability is lowered at low temperatures.
An object of the present invention is to provide a catalyst for producing a polyurethane exhibiting little odor, and a process for producing a polyurethane foam excellent in vinyl-staining resistance, fogging resistance and heat resistance, using the catalyst for producing a polyurethane.
Another object of the present invention is to provide a process capable of rapidly producing a polyurethane foam excellent in dimensional stability even under low-temperature surroundings with the generation of little odor based on the catalyst for producing a polyurethane.
These and other objects of the present invention will be apparent from the following description.
Specifically, the present invention relates to
(1) a catalyst for producing a polyurethane, comprising a dialkylaminoalkyl alcohol (hereinafter referred to as xe2x80x9cDAAAxe2x80x9d) represented by the formula (I):
R1R2Nxe2x80x94Xxe2x80x94OHxe2x80x83xe2x80x83(I) 
xe2x80x83wherein each of R1 and R2 is independently an alkyl group having 1 to 4 carbon atoms; and X is a branched alkylene group having 4 to 8 carbon atoms;
(2) a process for producing a polyurethane, comprising reacting a polyol component with an isocyanate component in the presence of a catalyst for producing a polyurethane, comprising the DAAA; and
(3) a process for producing a polyurethane foam, comprising reacting a polyol component with an isocyanate component in the presence of a catalyst for producing a polyurethane, comprising the DAAA, and a compound having a primary amino group and a tertiary amino group in its molecule (hereinafter referred to as xe2x80x9cFTA compoundxe2x80x9d) and a blowing agent.